You shouldn’t take the drawing literally. For once, energy levels of people with depression can differ a lot. It matters, whether you are in a low phase, whether you are severly depressed or can still function pretty well and so on. Also, there are other (chronic) illnesses that can do pretty much the same to your energy levels. I only wrote “depressed person“ though because depression is the only such thing that I have experience with. If you feel this graph is also accurate for your illness(es), cool! And third: It was difficult to name the top one because you can be depressed and have pretty good energy levels and you can be not healthy at all (say, have a broken leg), but still live with almost full energy. But you hopefully get what I want to express. Ooops, there is a fourth caveat: This explanation is what makes sense for me. I am not speaking for all people with depression. Here, you only get presented what one person with depression has to say.

So, on to the thing. For me it works to view being depressed like this: Usually, you should have the energy of the upper bar. At the beginning of a day, when you’ve slept well, the whole bar is full. Over the day, the green “daily energy“ part will get smaller. This happens faster if you’re stressed out and slower if you’re just relaxing. You can also somewhat recharge it by eating, drinking, resting, enjoyable freetime activities and so on. The green part starts out smaller if you haven’t slept well or if you are currently sick.
The “core energy“ part is usually not affected by usual daily activities. It gets smaller though, if you use up all of your daily energy and still keep going. It is used up slower, but it also recharges slower, so it’s not a good idea to scratch it at all. If you use it up until the red part, you are in survival mode. Everything gets really fucking hard, you are tired, you feel like shit. The closer you get to nothing in “core energy“, the less you can do until your body just refuses to deal. This is true for everyone, no matter whether you’re depressed or not.
Like I said, core energy only recharges slowly. If you’re in pretty good health, you can get out of the orange part by slowing down a bit for 2 to 3 days and giving yourself some special attention. The more you’ve used up, the more difficult it gets though to fully recharge it because usually life is in the way of, say, resting for 3 weeks.

Now, to when you’re depressed. Then you get the bar at the bottom. (How much of core energy and daily energy is left depends on the individual a lot. I just want to contrast the ideal energy of the upper bar with one example for depressed energy levels in the lower bar.) Like you can see, you start out the day with lower daily energy (even if you’ve slept okay) and your core energy is severly reduced. This leads to some pretty obvious problems: You can not do a lot in one day without using your daily energy up. If you’re severly depressed, you pretty much start out on core energy only. The other obvious problem: When your daily energy is gone (if there was any, to begin with) you are immediately dropping to the red part of the core energy. You are pretty fucked in other words. It gets difficult to do really basic things like: getting up, making decisions, make food, eat, getting out of bed, shower, put clothes on. There are advanced tasks you maybe won’t even be able to handle this day: getting out of the house, making a phone call, grocery shopping. And worst of all: You still have to do several of these things, for example to put food on the table, thus making it impossible for you to get rest, which would help recovering your core energy. Pretty fucked up, right?

So I hope this explanation is useful to some. I am aware that there may be a lot of parallels to chronic illness. Like I said above, I chose to make it about depression because it’s better to speak about things you get on a personal level. But if this makes sense to you, great.

What I forgot to mention: How is it possible that the core energy gets lower and lower for some people?It’s always about prolonged stress. This can either be a stressful time at work/in school or an abusive situation (microaggressions and discrimination and systemic oppression count), prolonged or chronic illness or a long and intense exam situation and so on. Everything that does not allow you to take care of your needs will erode the core energy over time. That is why it’s so difficult to get better in abusive situations: Your energy is always sapped even if you try to push back. Stress is still stress, even if you get used to it.